Power storage device comprising solid electrolyte layer over active material and second electrolyte and method of manufacturing the same

Abstract

An object is to provide a power storage device with improved cycle characteristics and a method of manufacturing the power storage device. Another object is to provide an application mode of the power storage device for which the above power storage device is used. In the method of manufacturing the power storage device, an active material layer is formed over a current collector, a solid electrolyte layer is formed over the active material layer after a natural oxide film over the active material layer is removed, and a liquid electrolyte is provided so as to be in contact with the solid electrolyte layer. Accordingly, decomposition and deterioration of the electrolyte solution which are caused by the contact between the active material layer and the electrolyte solution can be prevented, and cycle characteristics of the power storage device can be improved.

What is claimed is: 
     
       1. A method of manufacturing a power storage device, comprising the steps of:
 forming an active material layer comprising a silicon whisker over a current collector, the active material layer being formed by CVD method; 
 removing a natural oxide film over the active material layer; 
 forming a solid electrolyte layer over the active material layer by sputtering lithium iron phosphate after the natural oxide film is removed; and 
 providing a second electrolyte so as to be in contact with the solid electrolyte layer. 
 
     
     
       2. The method of manufacturing the power storage device, according to  claim 1 ,
 wherein the solid electrolyte layer is a layer comprising at least one of lithium phosphate, lithium manganese phosphate, lithium chromium phosphate, and lithium phosphorus sulfide. 
 
     
     
       3. The method of manufacturing the power storage device, according to  claim 1 ,
 wherein a thickness of the solid electrolyte layer is greater than or equal to 1 nm and less than or equal to 100 nm. 
 
     
     
       4. The method of manufacturing the power storage device, according to  claim 1 ,
 wherein the second electrolyte comprises:
 a first material selected from LiClO 4 , LiAsF 6 , LiBF 4 , LiPF 6 , and Li(C 2 F 5 SO 2 ) 2 N; and 
 a second material selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, a silicon gel, an acrylic gel, an acrylonitrile gel, a polyethylene oxide, a polypropylene oxide, and a fluorine-based polymer. 
 
 
     
     
       5. The method of manufacturing the power storage device according to  claim 1 ,
 wherein the silicon whisker is any of column-like shape, a cone-like shape, and a needle-like shape. 
 
     
     
       6. The method of manufacturing the power storage device, according to  claim 1 ,
 wherein the removing the natural oxide film over the active material layer is performed by any of reactive ion etching method, inductively coupled plasma etching method, and wet etching method. 
 
     
     
       7. The method of manufacturing the power storage device according to  claim 1 ,
 wherein the lithium iron phosphate has a NASICON structure. 
 
     
     
       8. The method of manufacturing the power storage device, according to  claim 1 ,
 wherein the current collector where the active material layer is formed by CVD method is used for a negative electrode, and 
 wherein the current collector is titanium. 
 
     
     
       9. A method of manufacturing a power storage device, comprising the steps of:
 forming an active material layer comprising a silicon whisker over a current collector, the active material layer being formed by CVD method; 
 removing a natural oxide film over the active material layer; 
 forming a solid electrolyte layer over the active material layer by sputtering lithium iron phosphate after the natural oxide film is removed; and 
 providing a liquid electrolyte so as to be in contact with the solid electrolyte layer. 
 
     
     
       10. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein the solid electrolyte layer is a layer comprising at least one of lithium phosphate, lithium manganese phosphate, lithium chromium phosphate, and lithium phosphorus sulfide. 
 
     
     
       11. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein a thickness of the solid electrolyte layer is greater than or equal to 1 nm and less than or equal to 100 nm. 
 
     
     
       12. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein the liquid electrolyte comprises:
 a first material selected from LiClO 4 , LiAsF 6 , LiBF 4 , LiPF 6 , and Li(C 2 F 5 SO 2 ) 2 N; and 
 a second material selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, a silicon gel, an acrylic gel, an acrylonitrile gel, a polyethylene oxide, a polypropylene oxide, and a fluorine-based polymer. 
 
 
     
     
       13. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein the silicon whisker is any of column-like shape, a cone-like shape, and a needle-like shape. 
 
     
     
       14. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein the removing the natural oxide film over the active material layer is performed by any of reactive ion etching method, inductively coupled plasma etching method, and wet etching method. 
 
     
     
       15. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein the lithium iron phosphate has a NASICON structure. 
 
     
     
       16. The method of manufacturing the power storage device, according to  claim 9 ,
 wherein the current collector where the active material layer is formed by CVD method is used for a negative electrode, and 
 wherein the current collector is titanium.